http://www.mdpi.com/journal/algorithms/special_issues/algorithmic_complexity/ Dear Colleagues, Is the universe computable, as suggested in the 1940s by Konrad Zuse, inventor of the first working program-controlled computer? With the ascent of virtual realities the idea has become popular, and is now also being taken seriously by physicists, for lack of contrarian physical evidence. Questions to be addressed in this special issue include: Which kind of programs running on which type of computational device could in principle provide a concise description of quantum physics? How can algorithmic complexity theory and Kolmogorov complexity theory guide the quest for simple explanations of the world in the sense of Occam's razor? How do Gödelian limits of mathematics and computation as well as insights from algorithmic information theory restrict the set of valid physical theories, including many world theories? Which sets of computable probability distributions or measures on possible universe histories make sense at all from the perspective of constructive mathematics? Following Solomonoff's theory of optimal inductive inference and algorithmic probability, how can the restrictions embodied by such sets help to predict future events, given past observations in a particular universe? Which testable predictions are made by algorithmic complexity-based theories of physics? Can we in principle design rational decision-making agents or artificial intelligences embedded in computable physics such that their decisions are optimal in reasonable mathematical senses? Which are the fundamental limitations of such decision makers? If physics is hard to compute, can this help to improve cryptography? Special Issue "In Memoriam Ray Solomonoff" (1926-2009): The Great Ray Solomonoff, pioneer of Machine Learning, founder of Algorithmic Probability Theory, father of the Universal Probability Distribution, creator of the Universal Theory of Inductive Inference, passed away on Monday 7 December 2009 at age 83. Ray Solomonoff was the first to describe the fundamental concept of Algorithmic Information or Kolmogorov Complexity. In the new millennium his work became the foundation of the first mathematical theory of Optimal Universal Artificial Intelligence. With great sadness the special issue will be "In Memoriam Ray Solomonoff". Prof. Dr. Juergen Schmidhuber Guest Editor Submission All papers should be submitted to algorithms@mdpi.org. To be published continuously until the deadline and papers will be listed together at the special issue website. Submitted papers should not have been published nor be under consideration for publication elsewhere. All papers are refereed through a peer-review process. A guide for authors is available on the Instructions for Authors page. Algorithms is an international peer-reviewed quarterly journal published by Molecular Diversity Preservation International. Article Processing Charges (APC) will be waived for well prepared manuscripts of invited papers. For the first three volumes of this new journal the APC are of 300 CHF (or 550 CHF per paper for those papers that require extensive additional formatting and/or English corrections) for papers submitted before 31 December 2010. http://www.mdpi.com/1999-4893/2/3/879/ Specialized intelligent systems can be found everywhere: finger print, handwriting, speech, and face recognition, spam filtering, chess and other game programs, robots, et al. This decade the first presumably complete mathematical theory of artificial intelligence based on universal induction-prediction-decision-action has been proposed. This informationtheoretic approach solidifies the foundations of inductive inference and artificial intelligence. Getting the foundations right usually marks a significant progress and maturing of a field. The theory provides a gold standard and guidance for researchers working on intelligent algorithms. The roots of universal induction have been laid exactly half-a-century ago and the roots of universal intelligence exactly one decade ago. So it is timely to take stock of what has been achieved and what remains to be done. Since there are already good recent surveys, I describe the state-of-the-art only in passing and refer the reader to the literature. This article concentrates on the open problems in universal induction and its extension to universal intelligence. http://www.mdpi.com/1999-4893/2/3/879/ Thu, 02 Jul 2009 00:00:00 CEST Algorithms 2009-07-02 2 3 Article 879 906 1999-4893 Open Problems in Universal Induction & Intelligence 2009-07-02 doi: 10.3390/a2030879 Marcus Hutter